Calculating pump to cylinder pressure ratios

[Dohcdelsol93]

This may not be the proper forum but i need to find a way to calculate how much effort it will take to move a cylinder using a manual helm pump.

The hydraulic cylinder i intend on using is a 32mm bore with a 16mm diameter. Stroke of 178mm. Volume of 107 cc

The helm pump (attaches to a steering wheel so you power the system)

I've got two options at helm pump i believe would work.One is a 23cc pump

The other is a 27.8 cc

The maximum steering wheel diameter is 20 inches. Id like as small as possible.

Im not sure what other specs i need to get for this calculation. The goal is to make steering easy with one or two fingers.

The cylinder will be pushing an inboard/outboard 260hp fooot back and forth for steering. About 7 turns is the maximum i want to turn from clock to clock

Thank you for your time

 

[sophiecentaur]

Hi and welcome to PF. I reckon this is the right forum for your question.
I apologise if you know these basics but I wonder if the information you have given is enough to get an answer.
What is the force / torque you need to apply to your drive and what range of angle? (Let's say Force and length of throw) To give yourself a mechanical advantage of MA, the ratio of movement (length of throw) to the distance moved around the wheel (total angle times radius) must be at least 1/ MA. I searched "Helm Pumps" and there are a lot of manufacturers' links. This one describes the basic mechanical requirements. But you have to know a figure for the required force on the ram. That could be obtained from the manufacturers, I am sure. I would also suggest that the beltway forward would be to take advice from a supplier or look at arrangements on other boats; it's probably fairly standard, once you have specified the engine / drive system. I imagine this stuff is not cheap so you don't want to spend too much or find your system is not adequate and then have to replace it. My only boat steering experience has been a tiller on a sailing cruiser and it had been designed so that the tiller length was suitable for the boat, sails and rudder size. The force to operate it sometimes was a lot more than "easy for two fingers" With a drive, I would imagine that balance was critical - so knowing the engine spec would be essential.